Tasas de acreción y características de los sedimentos actuales en el parque nacional Las Tablas de Daimiel (Ciudad Real)

Abstract

Accretion rates in Las Tablas de Daimiel National Park are very high (2.38 ± 1.93 cm year^-1) compared to those of other wetlands. Sediment deposition decreases significantly toward the wetland outlet which is related to bed roughness, water level and macrophyte cover. Sediments are different in each wetland zone, owing to hydrodynamic and biotic characteristics: while silt accumulates mainly in channels, sand is the dominant fraction in lentic zones (deep and shallow) with or without vegetation. On a temporal scale, accretion rates increase toward autumn and winter, coinciding with plant senescence and decay. The accumulated sediment bears a high content of autochthonous mineral matter (31-57 %), which proceeds either from fast mineralisation of the deposited organic residues and/or from the endogenous precipitation of calcite, which is the predominating mineral phase. The deposited organic matter also originates from autochthonous sources (45-65 %) and proceeds of emergent vegetation decay. Finally, we present a simulation of the sedimentary evolution of the wetland for the next century, which demonstrates its filling up and disappearance if current accretion rates are maintained.